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Old November 1st 03, 12:30 AM
 
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Default 40M+80M dual band delta loop?

Hi group,
just wondering.... can I take a 40M delta loop and add an 80M dipole to it?
Will there be interaction?
SWR problems?

Mark W4UDX



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Old November 1st 03, 01:28 AM
'Doc
 
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Mark,
Yes, to both.
'Doc
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Old November 5th 03, 07:25 PM
Desmoface
 
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just wondering.... can I take a 40M delta loop and add an 80M dipole to it?
Will there be interaction? SWR problems?


Why not just increase the size of your loop to make it an 80 meter loop?? That
should cover 40m, at least thats what I've read...I'm in the process of
building my 80 meter loop which will hopefully work 10-80...Good luck..

Steve

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Old November 6th 03, 04:48 PM
Dan/W4NTI
 
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"Desmoface" wrote in message
...
just wondering.... can I take a 40M delta loop and add an 80M dipole to

it?
Will there be interaction? SWR problems?


Why not just increase the size of your loop to make it an 80 meter loop??

That
should cover 40m, at least thats what I've read...I'm in the process of
building my 80 meter loop which will hopefully work 10-80...Good luck..

Steve


But remember a loop for 80 fed with coax will make for a high impedeance on
40.

If you feed this 80 meter loop with ladder line, open wire line, etc. You
can use it everywhere via a balanced output tuner of course.

Dan/W4NTI




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Old November 6th 03, 05:09 PM
Cecil Moore
 
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Dan/W4NTI wrote:
But remember a loop for 80 fed with coax will make for a high impedeance on
40.


Higher, but not too high. A 2 WL loop is resonant in much the same way
that a 1 WL loop is resonant. Perhaps you are thinking about dipoles?
--
73, Cecil http://www.qsl.net/w5dxp



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Old November 6th 03, 07:07 PM
Desmoface
 
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But remember a loop for 80 fed with coax will make for a high impedeance on
40.


Yeah, you'd probably need to use a tuner but one wavelength on 80 is 2
wavelengths on 40, is 4 wl's on 20, 8 on 10....theoretically an 80 meter loop
should work great on 10-80 and the take off angle supposedly decreases as the
frequency increases...so it should be good at dx too..

Steve
kb8viv
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Old November 6th 03, 07:14 PM
Tarmo Tammaru
 
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"Cecil Moore" wrote in message
...
Dan/W4NTI wrote:
But remember a loop for 80 fed with coax will make for a high impedeance

on
40.


Higher, but not too high. A 2 WL loop is resonant in much the same way
that a 1 WL loop is resonant. Perhaps you are thinking about dipoles?
--
73, Cecil http://www.qsl.net/w5dxp


Two things to consider he

1. If you cut it for 3850, as an example, it will be way out of band on 40
meters (7700).

2. If you match it with a 1/4 wave section of RG11 on 80 meters, that will
be 1/2 wave on 40, and have no effect.

Having said all that, I find my Ameritron amp with a pi network output will
tune up on 40 meters. My loop is resonant at about 3800. Just in case, I
keep the power down.

Tam/WB2TT


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Old November 6th 03, 07:33 PM
Desmoface
 
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1. If you cut it for 3850, as an example, it will be way out of band on 40
meters (7700).


Will it?? A full wave on 3850 is aprox 261 ft. A full wave on 7700 is aprox
130.52 feet. Looks pretty close to 2 wavelengths on 40..using the 1005/Freq
loop equation..

Again, my loop isnt up yet so I can't comment, I'm just going by equations on
paper...I'd expect a 2:1-3:1 swr on its resonant frq as it should see aprox 100
ohms....easily tuned out with the built in tuner in my rig...I would expect it
to work pretty good on 10-80 but will most certainly need a tuner to keep the
finals happy on freq's above 80....This is what I'm banking on LOL...Mine
should be up saturday..WOOHOO!!

Steve
kb8viv


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Old November 6th 03, 07:39 PM
Desmoface
 
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Will it?? A full wave on 3850 is aprox 261 ft. A full wave on 7700 is aprox
130.52 feet. Looks pretty close to 2 wavelengths on 40..using the 1005/Freq
loop equation..


Woops, this is the eqation for a loop, not sure if it applies to a delta
loop..but it shouldnt be far off...

Steve
kb8viv


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